GB2187223A

GB2187223A - Process and device for tunnel drilling reconnaissance

Info

Publication number: GB2187223A
Application number: GB08704186A
Authority: GB
Inventors: Raymond Rami
Original assignee: Soletanche SA
Current assignee: Soletanche SA
Priority date: 1986-02-24
Filing date: 1987-02-23
Publication date: 1987-09-03
Also published as: FR2594884A1; FR2594884B1; GB2187223B; JPS62296093A; GB8704186D0

Abstract

The invention relates to a process for carrying out reconnaissance during advance work in the drilling of a tunnel, of the type in which a hole (6) of small diameter, inside which a tube (1) intended for receiving an obstructor (9) is engaged, is drilled ahead of the working face (5). A tube (1) equipped on its outer surface with at least one helical rib (2) is inserted into the drill-hole (6) from the tunnel, a rotation and an axial advance corresponding to the pitch of the helical rib or helical ribs (2) being imparted to the said tube, so that the said rib or ribs (2) engage into the rock (7) surrounding the said drill-hole (6), disturbing its structure as little as possible. <IMAGE>

Description

SPECIFICATION Process and device for tunnel drilling reconnaissance The present invention-relatesto a process for carrying out reconnaissance during advance work in the drilling of a tunnel and to a device for carrying out this process.

It is known that, during the drilling of a tunnel, the nature of the rock ahead of the working face has to be reconnoitred, in such a way asto detect variations in the nature of the rock in which the tunnel is drilled and large waterways which could put safety at risk, if the drilling ofthe tunnel were continued in these zones, without the necessary consolidating or sealing work having been carried out beforehand.

Atthe presenttime, such reconnaissances are made by drilling a hole of small diameter in the direction of the tunnel over a length of a few tens of metres, so that it is possible to determine the nature ofthe rock and possible waterways.

If this reconnaissance drilling encounters a waterway with a substantial flow, it must be possible to shut offthe reconnaissance drill-hole, in orderto prevent the flow ofthis water from carrying away inside the tunnel some of the rock located near the working face round the hole.

For this purpose, simple metal tubes are generally used, and these are engaged forceably or bedded in the drill-hole and can receive an obstructor consisting, for example, of an inflatable bag, so asto preventthe water from flowing into the tunnel.

This procedure is not entirely satisfactory, because, on the one hand, water leaks which can be considerable sometimes occur between the outside ofthetube and the rock, and, on the other hand, the hydrostatic pressure exerted on the obstructor located insidethe tube generates a high axial force which in some cases can expel the tube from the rock, pushing it into the tunnel, with all the risks which that implies.

The process and the device according to the invention make it possible to overcome this disadvantage in a simple and effective way.

The subject ofthe present invention is a process for carrying out reconnaissance during advance work in the drilling of a tunnel, ofthetypein which a hole of small diameter, inside which a tube intended for receiving an obstructor is engaged, is drilled ahead of the working face, characterized in that a tube equipped on its outer surface with at least one helical rib is inserted into the drill-hole from the tunnel, a rotation and an axial advance corresponding to the pitch of the helical rib or helical ribs some being imparted to the said tube, so thatthe said rib or ribs engage into the rock surrounding the said drill-hole, disturbing its structure as little as possible.

It\luill be seen that, according to the invention, the twofold advantage of the helical rib or-he1ical ribs is" ontheen41:rand, eff'ctfvei:y to prevent longitudimal:: waterleakswbich,inthe state of earts QCCUF occur between the rock anew the outer surface dtiretube and, on the other hand,to anchorthetubefirmly in the rock surrounding it, thus ensuring that, when the obstructorlocated inside thetube is subjected to a strong axial th rust attri buta ble to the water pressure, the tube according to the invention does not risk being ejected from the rock.

The subject of the present invention is also a tube for carrying out the process mentioned above, characterized in that it has at least one helical rib on its outer surface.

The tube according to the invention preferably has a bevel in its front part, so that it can be engaged into the rock more easily.

The tube according to the invention can also be produced in several sections connected to one another, for example, by means of key-and-slot devices.

To make iteasyto understandthe invention, an embodiment taken as an example and illustrated in the drawing will now be described byway of illustration and in a non-limiting way.

In this drawing: - Figure 1 is elevation view of a tube according to the invention, equipped with a helical rib, - Figure 2 is a diagrammatic view showing howthe process according to the invention is carried out.

Figure 1 showsthetube 1 equipped with a helical rib 2 which can consist, for example, of a metal sheet of suitable shape welded to the outside of the tube 1.

lntheembodimentillustrated,thetubehasasingle rib 2, but it is clearthatthe scope of the invention would not be exceeded if several ribswere provided.

Likewise, although preferred, it is not essential that the rib 2 be formed continuously overthe entire length of the tube, and in some cases, for the sake of simpler production, it is merely necessary to weld rib sections of limited length to the periphery of the tube.

Atthe left-hand end ofthetube shown in Figure 1, it is possible to seethe bevel 3which makes it possible to insertthetube according to the invention more easily into the previously drilled hole 6.

Also shown diagrammatically on the right-hand side of Figure lisa recess 4which is provided on each side of the tube and which makes it possible to connectthetubesection illustrated in Figure 1 to another section, for example by means of a key-andslot device (not shown).

Figure 2 is a diagrammtic view showing how the process according to the invention is carried out.

It illustrates, once again, the tube 1 which is equipped with helical ribs 2 and which has been engaged, from the working face 5 of the tunnel, into the reconnaissance drill-hole 6 made in the rock 7 ahead oftheworking face.

In this Figure 2, which is a diagrammtic representa tion,thetube 1 andthedrill-hole6 have been shown shorterthan in actual fact.

The tube 1 according to the invention is put in position from the working face 5 by introducing the front end 3 of the tube into the drill-hole 6 and subjecting the tube 1 to an advancing movement which is proportional to a rotational movement imparted to it and which corresponds to the pitch of tbe helical: rib, sothat the latter penetrates into the rock 7, breaking itup as little as possible.

tf desired, several successive sections oftubes 1 can be used, ifthey are connected by means of a device subjecting them to a common rotation.

If a waterway is discovered during drilling, it is sufficient, afterthe drill-rod has been removed, to introduce inside the tube 1 put in position since the start of drilling a tube 8 of small diameter having, at its end, an inflatable obstructor 9 which comes up against the innerwalls of the tube 1 when, for example, water is injected insidethetube 8.

The drill-hole 6 is shut off effectively in this way, and despite the high hydrostatic forces which can be exerted on the obstructor9 and consequently on the tube 1,the latter, which is firmly anchored in the rock7 by means ofthe helical ribs 2, does not risk being ejected into the tunnel, which would present a definite danger Moreover, the water leaks which could occur along the outside of the tube are virtually eliminated because they have to run round a considerable number of ribs, and this results in substantial pressure losses.

ltcan beseen thatthedevice according to the invention makes it possible, in a particular simple and economical way, to improve the execution of reconnaissance drilling during advance work in the digging oftunnels It goes without saying thatthe embodimentde- scribed is in no way limiting, and that it can undergo any desirable modifications, without thereby departingfrom the scope ofthe invention.

Claims

1. Processforcarrying out reconnaissance during advance work in-the drilling of a tunnel, of the tupe in which a hole of small diameter, inside which a tube intendedfor receiving an obstructor is engaged, is drilled ahead ofthe working face, characterized in that a tube equipped on its outersurface with at least one helical rib is inserted into the drill-hole from the tunnel, a rotation and an axial advance corresponding to the pitch of the helical rib or helical ribs being imparted to the said tube, so thatthe said rib or ribs engage into the rock surrounding the said drill-hole, disturbing its structure as little as possible.

2. Deviceforcarrying out the process accordingto Claim 1, characterized in that it consists of a tube having at leastone helical rib on its outer surface.

3. Device according to Claim 2, characterized in that it has a bevel in itsfront part.

4. Device according to Claim 1 or2,characterized in that itis produced in several sections connected to one another, for example, by means of key-and-slot devices.